Just use fun[0]==0 to indicate a bad itab.
Change-Id: I28ecb2d2d857090c1ecc40b1d1866ac24a844848
Reviewed-on: https://go-review.googlesource.com/44473
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Keep itabs in a growable hash table.
Use a simple open-addressable hash table, quadratic probing, power
of two sized.
Synchronization gets a bit more tricky. The common read path now
has two atomic reads, one to get the table pointer and one to read
the entry out of the table.
I set the max load factor to 75%, kind of arbitrarily. There's a
space-speed tradeoff here, and I'm not sure where we should land.
Because we use open addressing the itab.link field is no longer needed.
I'll remove it in a separate CL.
Fixes#20505
Change-Id: Ifb3d9a337512d6cf968c1fceb1eeaf89559afebf
Reviewed-on: https://go-review.googlesource.com/44472
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Last runtime use was removed in https://golang.org/cl/133700043,
September 2014.
Replace plan9 syscall uses with plan9-specific variable.
Change-Id: Ifb910c021c1419a7c782959f90b054ed600d9e19
Reviewed-on: https://go-review.googlesource.com/55450
Reviewed-by: Martin Möhrmann <moehrmann@google.com>
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
The preceding cleanup made it clear that two cases
(have golden data, unreachable key) are handled identically.
Simplify the control flow to reflect that.
Simplifies the code and generates shorter machine code.
Change-Id: Id612e0da6679813e855506f47222c58ea6497d70
Reviewed-on: https://go-review.googlesource.com/55093
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This change unifies the x and y cases.
It shrinks evacuate's machine code by ~25% and its stack size by ~15%.
It also eliminates a critical branch.
Whether an entry should go to x or y is designed to be unpredictable.
As a result, half of the branch predictions for useX were wrong.
Mispredicting that branch can easily incur an expensive cache miss.
Switching to an xy array allows elimination of that branch,
which in turn reduces cache misses.
Change-Id: Ie9cef53744b96c724c377ac0985b487fc50b49b1
Reviewed-on: https://go-review.googlesource.com/54653
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Make the calculation of k and v a bit lazier.
None of the following code cares about indirect-vs-direct k,
and it happens on all code paths, so check t.indirectkey earlier.
Simplifies the code and reduces both machine code and stack size.
Change-Id: I5ea4c0772848d7a4b15383baedb9a1f7feb47201
Reviewed-on: https://go-review.googlesource.com/55092
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This avoids division and multiplication.
Instrumentation suggests that this is a very common case.
Change-Id: I2d5d5012d4f4df4c4af1f9f85ca9c323c9889c0e
Reviewed-on: https://go-review.googlesource.com/54657
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This avoids the never triggered capacity checks in newarray.
Change-Id: Ib72b204adcb9e3fd3ab963defe0cd40e22d5d492
Reviewed-on: https://go-review.googlesource.com/54731
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This makes sure that its argument is marked live on entry.
We need its arg to be live so defers of KeepAlive get
scanned correctly by the GC.
Fixes#21402
Change-Id: I906813e433d0e9726ca46483723303338da5b4d7
Reviewed-on: https://go-review.googlesource.com/55150
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This change replaces the current runtime capabilities check for ppc64x with the
new internal/cpu package. It also adds support for the new POWER9 ISA and
capabilities.
Updates #15403
Change-Id: I5b64a79e782f8da3603e5529600434f602986292
Reviewed-on: https://go-review.googlesource.com/53830
Reviewed-by: Martin Möhrmann <moehrmann@google.com>
This generates better code.
Masking B in the return statement should be unnecessary,
but the compiler is understandably not yet clever enough to see that.
Someday, it'd also be nice for the compiler to generate
a CMOV for the saturation if statement.
Change-Id: Ie1c157b21f5212610da1f3c7823a93816b3b61b9
Reviewed-on: https://go-review.googlesource.com/54656
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>
Combine conditions into a single if statement.
This is more readable.
It should generate identical machine code, but it doesn't.
The new code is shorter.
Change-Id: I9bf52f8f288b0df97a2b9b4e4183f6ca74175e8a
Reviewed-on: https://go-review.googlesource.com/54651
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>
This reduces the wall time to run these benchmarks by about 30%.
Change-Id: I494a93c93e5acb1514510d85f65796f62e1629a5
Reviewed-on: https://go-review.googlesource.com/54650
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>
Currently we only support finding symbols in the VDSO using the old
DT_HASH. These days everything uses DT_GNU_HASH instead. To keep up
with the times and future-proof against DT_HASH disappearing from the
VDSO in the future, this commit adds support for DT_GNU_HASH and
prefers it over DT_HASH.
Tested by making sure it found a DT_GNU_HASH section and all of the
expected symbols in it, and then disabling the DT_GNU_HASH path and
making sure the old DT_HASH path still found all of the symbols.
Fixes#19649.
Change-Id: I508c8b35a019330d2c32f04f3833b69cb2686f13
Reviewed-on: https://go-review.googlesource.com/45511
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The dieFromSignal runtime function attempts to forward crashing
signals to a signal handler registered before the runtime was
initialized, if any. However, on Darwin, a special signal handler
trampoline is invoked, even for non-Go signal handlers.
Clear the crashing signal's handlingSig entry to ensure sigtramp
forwards the signal.
Fixes the darwin/386 builder.
Updates #20392
Updates #19389
Change-Id: I441a3d30c672cdb21ed6d8f1e1322d7c0e5b9669
Reviewed-on: https://go-review.googlesource.com/55032
Run-TryBot: Elias Naur <elias.naur@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
According to http://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_key_create.html,
pthread_key_create return an error number which is greater than or equal
to 0. I don't know the scenario that pthread_setspecific would fail, but
also don't know the future. Add some error handlings just in case.
Change-Id: I0774b79ef658d67e300f4a9aab1f2e3879acc7ee
Reviewed-on: https://go-review.googlesource.com/54811
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
_main has an early check to verify if a binary is statically or dynamically
linked that depends on R0 being zero. R0 is not guaranteed to be zero at that
point and this was breaking Go on Alpine for ppc64le.
Change-Id: I4a1059ff7fd3db6fc489e7dcfe631c1814dd965b
Reviewed-on: https://go-review.googlesource.com/54730
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
Although mincore is declared in stubs.go, mincore isn't used by any
OSes except linux. Move it to os_linux.go and clean up unused code.
Change-Id: I6cfb0fed85c0317a4d091a2722ac55fa79fc7c9a
Reviewed-on: https://go-review.googlesource.com/54910
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This computes the maximum possible waste in a size class due to both
internal and external fragmentation as a percent of the span size.
This parallels the reasoning about overhead in the comment at the top
of mksizeclasses.go and confirms that comment's assertion that (except
for the few smallest size classes), none of the size classes have
worst-case internal and external fragmentation simultaneously.
Change-Id: Idb66fe6c241d56f33d391831d4cd5a626955562b
Reviewed-on: https://go-review.googlesource.com/49370
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Before this CL, whenever the Go runtime wanted to kill its own
process with a signal dieFromSignal would reset the signal handler
to _SIG_DFL.
Unfortunately, if any signal handler were installed before the Go
runtime initialized, it wouldn't be invoked either.
Instead, use whatever signal handler was installed before
initialization.
The motivating use case is Crashlytics on Android. Before this CL,
Crashlytics would not consider a crash from a panic() since the
corresponding SIGABRT never reached its signal handler.
Updates #11382
Updates #20392 (perhaps even fixes it)
Fixes#19389
Change-Id: I0c8633329433b45cbb3b16571bea227e38e8be2e
Reviewed-on: https://go-review.googlesource.com/49590
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
To avoid gigantic core dumps, the runtime avoids raising SIGABRT
on crashes on 64-bit Darwin systems. Mobile OS'es (probably) don't
generate huge core dumps, so to aid crash reporters, allow SIGABRT
on crashes on darwin/arm64.
Change-Id: I4a29608f400967d76f9bd0643fea22244c2da9df
Reviewed-on: https://go-review.googlesource.com/49770
Run-TryBot: Elias Naur <elias.naur@gmail.com>
Reviewed-by: Avelino <t@avelino.xxx>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This change enables buildmode c-shared on ppc64le.
A bug was fixed in runtime/rt0_linux_ppc64le.s that was necessary to
make this work. In _rt0_ppc64le_linux_lib, there is code to store
the value of r2 onto the caller's stack. However, if this file
is compiled using a build mode that maintains the TOC address in
r2, then instructions will be inserted at the beginning of this
function to generate the r2 value for the callee, not the caller.
That means the r2 value for the callee is stored onto the caller's
stack. If caller and callee don't have the same r2 values, then
the caller will restore the wrong r2 value after it returns. This
situation can happen when using dlopen since the caller of this
function will be in ld64.so and will definitely have a different
TOC.
Updates #20756
Change-Id: I6e165e0d0716e73721bbbcc520e8302e4856e3ba
Reviewed-on: https://go-review.googlesource.com/53890
Reviewed-by: Ian Lance Taylor <iant@golang.org>
We use lock-free reads from mheap.spans, but the safety of these is
somewhat subtle. Document this.
Change-Id: I928c893232176135308e38bed788d5f84ff11533
Reviewed-on: https://go-review.googlesource.com/54310
Reviewed-by: Rick Hudson <rlh@golang.org>
The compiler is now smart enough not to insert a bounds check.
Not only is this simpler, it eliminates a LEAQ from the
generated code.
Change-Id: Ie90cbd11584542edd99edd5456d9b02c406e8063
Reviewed-on: https://go-review.googlesource.com/53892
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
It appears that this was just missed
by accident in the original implementation.
Change-Id: Id87147bcb7a685d624eac7034342a305ad644e7a
Reviewed-on: https://go-review.googlesource.com/53891
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Avelino <t@avelino.xxx>
According to http://infocenter.arm.com:
* ARM Cortex-A53 (Raspberry Pi 3, Pine A64)
* ARM Cortex-A57 (Opteron A1100, Tegra X1)
* ARM Cortex-A72
all have a cache line size of 64 bytes.
Change-Id: I4b333e930792fb1a221b3ca6f395bfa1b7762afa
Reviewed-on: https://go-review.googlesource.com/43250
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
The only non test user of the assembler prefetch functions is the
heapBits.prefetch function which is itself unused.
The runtime prefetch functions have no functionality on most platforms
and are not inlineable since they are written in assembler. The function
call overhead eliminates the performance gains that could be achieved with
prefetching and would degrade performance for platforms where the functions
are no-ops.
If prefetch functions are needed back again later they can be improved
by avoiding the function call overhead and implementing them as intrinsics.
Change-Id: I52c553cf3607ffe09f0441c6e7a0a818cb21117d
Reviewed-on: https://go-review.googlesource.com/44370
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
We need to make sure that when the key contains a pointer, we use
a write barrier to update the key.
Also mapdelete_* should use typedmemclr.
Fixes#21297
Change-Id: I63dc90bec1cb909c2c6e08676c9ec853d736cdf8
Reviewed-on: https://go-review.googlesource.com/53414
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The activeModules function is called by the cgo pointer checking code,
which is called by the write barrier (when GODEBUG=cgocheck=2), and as
such must be nosplit/nowritebarrier.
Fixes#21306
Change-Id: I57f2124f14de7f3872b2de9532abab15df95d45a
Reviewed-on: https://go-review.googlesource.com/53352
Reviewed-by: Austin Clements <austin@google.com>
We lazily map the bitmap and spans areas as the heap grows. However,
right now we're very slightly too lazy. Specifically, the following
can happen on 32-bit:
1. mallocinit fails to allocate any heap arena, so
arena_used == arena_alloc == arena_end == bitmap.
2. There's less than 256MB between the end of the bitmap mapping and
the next mapping.
3. On the first allocation, mheap.sysAlloc sees that there's not
enough room in [arena_alloc, arena_end) because there's no room at
all. It gets a 256MB mapping from somewhere *lower* in the address
space than arena_used and sets arena_alloc and arena_end to this
hole.
4. Since the new arena_alloc is lower than arena_used, mheap.sysAlloc
doesn't bother to call mheap.setArenaUsed, so we still don't have a
bitmap mapping or a spans array mapping.
5. mheap.grow, which called mheap.sysAlloc, attempts to fill in the
spans array and crashes.
Fix this by mapping the metadata regions for the initial arena_used
when the heap is initialized, rather than trying to wait for an
allocation. This maintains the intended invariant that the structures
are always mapped for [arena_start, arena_used).
Fixes#21044.
Change-Id: I4422375a6e234b9f979d22135fc63ae3395946b0
Reviewed-on: https://go-review.googlesource.com/51714
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Right now, if it's possible to grow the arena reservation but
mheap.sysAlloc fails to get 256MB more of memory, it simply fails.
However, on 32-bit we have a fallback path that uses much smaller
mmaps that could take in this situation, but fail to.
This commit fixes mheap.sysAlloc to use a common failure path in case
it can't grow the reservation. On 32-bit, this path includes the
fallback.
Ideally, mheap.sysAlloc would attempt smaller reservation growths
first, but taking the fallback path is a simple change for Go 1.9.
Updates #21044 (fixes one of two issues).
Change-Id: I1e0035ffba986c3551479d5742809e43da5e7c73
Reviewed-on: https://go-review.googlesource.com/51713
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
64bit atomics on mips/mipsle are implemented using spinlocks. If SIGPROF
is received while the program is in the critical section, it will try to
write the sample using the same spinlock, creating a deadloop.
Prevent it by creating a counter of SIGPROFs during atomic64 and
postpone writing the sample(s) until called from elsewhere, with
pc set to _LostSIGPROFDuringAtomic64.
Added a test case, per Cherry's suggestion. Works around #20146.
Change-Id: Icff504180bae4ee83d78b19c0d9d6a80097087f9
Reviewed-on: https://go-review.googlesource.com/42652
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
The runtime tests may be invoked from a parent that has SIGQUIT
blocked. For example, Java invokes subprocesses this way. In this
situation, TestCrashDumpsAllThreads and TestPanicSystemstack will fail
because they depend on SIGQUIT to get tracebacks, and any subprocess
test that times out will fail to kill the subprocess.
Fix this by detecting if SIGQUIT is blocked and, if so, skipping tests
that depend on it and using SIGKILL to kill timed-out subprocesses.
Based on a fix by Carl Henrik Lunde in
https://golang.org/issue/19196#issuecomment-316145733Fixes#19196.
Change-Id: Ia20bf15b96086487d0ef6b75239dcc260c21714c
Reviewed-on: https://go-review.googlesource.com/50330
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
If we are using vfork, and if something (such as TSAN) is intercepting
the sigaction function, then we must call the system call, not the
libc function. Otherwise the intercepted sigaction call in the child
may trash the data structures in the parent.
Change-Id: Id9588bfeaa934f32c920bf829c5839be5cacf243
Reviewed-on: https://go-review.googlesource.com/50251
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Reviewed-by: Austin Clements <austin@google.com>
Currently we trace mark assists even if they're satisfied entirely by
stealing. This means even if background marking is keeping up with
allocation, we'll still emit a trace event every N bytes of
allocation. The event will be a few microseconds, if that, but they're
frequent enough that, when zoomed out in the trace view, it looks like
all of the time is spent in mark assists even if almost none is.
Change this so we only emit a trace event if the assist actually has
to do assisting. This makes the traces of these events far more
useful.
Change-Id: If4aed1c413b814341ef2fba61d2f10751d00451b
Reviewed-on: https://go-review.googlesource.com/50030
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Rick Hudson <rlh@golang.org>
tSweepTerm and pauseStart are supposed to be when STW was triggered,
but right now they're captured a bit before STW. Move these down to
immediately before we trigger STW.
Fixes#19590.
Change-Id: Icd48a5c4d45c9b36187ff986e4f178b5064556c1
Reviewed-on: https://go-review.googlesource.com/49612
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Currently, Windows stacks are either 128kB or 2MB depending on whether
the binary uses cgo. This is because we assume that Go system stacks
and the small amount of C code invoked by the standard library can
operate within smaller stacks, but general Windows C code assumes
larger stacks.
However, it's easy to call into arbitrary C code using the syscall
package on Windows without ever importing cgo into a binary. Such
binaries need larger system stacks even though they don't use cgo.
Fix this on 64-bit by increasing the system stack size to 2MB always.
This only costs address space, which is free enough on 64-bit to not
worry about. We keep (for now) the existing heuristic on 32-bit, where
address space comes at more of a premium.
Updates #20975.
Change-Id: Iaaaa9a2fcbadc825cddc797aaaea8d34ef8debf2
Reviewed-on: https://go-review.googlesource.com/49331
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
kicking off contributing again with a classic
Change-Id: Ifb0aed8f1dc854f85751ce0495967a3c4315128d
Reviewed-on: https://go-review.googlesource.com/49016
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
It seems that when too much other code is running on the system,
the testprogcgo code can overrun its timeouts.
Updates #18598.
Not marking the issue as fixed until it doesn't recur for some time.
Change-Id: Ieaf106b41986fdda76b1d027bb9d5e3fb805cc3b
Reviewed-on: https://go-review.googlesource.com/48233
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
SysV semaphore undo lists should be shared by threads, just like
several other resources listed in cloneFlags. Currently we don't do
this, but it probably doesn't affect anything because 1) probably
nobody uses SysV semaphores from Go and 2) Go-created threads never
exit until the process does. Beyond being the right thing to do,
user-level QEMU requires this flag because it depends on glibc to
create new threads and glibc uses this flag.
Fixes#20763.
Change-Id: I1d1dafec53ed87e0f4d4d432b945e8e68bb72dcd
Reviewed-on: https://go-review.googlesource.com/48170
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TestStackGrowth is currently a parallel test. However, it depends on a
20 second timeout, which is already dubious in a parallel test, and
became really problematic on slow builders when runtime.GC switched to
triggering concurrent GC instead of STW GC. Before that change, the
test spent much of its time in STW GC, so it wasn't *really* parallel.
After that change, it was competing with all of the other parallel
tests and GC likely started taking ~4 times longer. On most builders
the whole test runs in well under a second, but on the slow builders
that was enough to push it over the 20 second timeout.
Fix this by making the test serial.
Updates #19381 (probably fixes it, but we'll have to wait and see).
Change-Id: I21af7cf543ab07f1ec1c930bfcb355b0df75672d
Reviewed-on: https://go-review.googlesource.com/48110
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Elias Naur <elias.naur@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
The current description refers to the outermost "frame" which can be
misleading. A user reading it can think it means a stack frame.
Change-Id: Ie2c7cb4b4db8f41572df206478ce3b46a0245a5d
Reviewed-on: https://go-review.googlesource.com/47850
Reviewed-by: Austin Clements <austin@google.com>
Currently, sysmon waits 60 ms during idle before relaxing. This is
primarily to avoid reducing the precision of short-duration timers. Of
course, if there are no short-duration timers, this wastes 60 ms
running the timer at high resolution.
Improve this by instead inspecting the time until the next timer fires
and relaxing the timer resolution immediately if the next timer won't
fire for a while.
Updates #20937.
Change-Id: If4ad0a565b65a9b3e8c4cdc2eff1486968c79f24
Reviewed-on: https://go-review.googlesource.com/47833
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Currently, sysmon relaxes the Windows timer resolution as soon as the
Go process becomes idle. However, if it's going idle because of a
short sleep (< 15.6 ms), this can turn that short sleep into a long
sleep (15.6 ms).
To address this, wait for 60 ms of idleness before relaxing the timer
resolution. It would be better to check the time until the next wakeup
and relax immediately if it makes sense, but there's currently no
interaction between sysmon and the timer subsystem, so adding this
simple delay is a much simpler and safer change for late in the
release cycle.
Fixes#20937.
Change-Id: I817db24c3bdfa06dba04b7bc197cfd554363c379
Reviewed-on: https://go-review.googlesource.com/47832
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
R11 is callee-save in the C ABI, but the temporary register in the Go
ABI. Currently it's being clobbered by runtime.addmoduledata, which
has to follow the C ABI. The observed effect of this was that
dl_open_worker was returning to a bad PC because after it failed to
restore its SP because it was using R11 as a frame pointer.
Fix this by saving R11 around addmoduledata.
Fixes#19674.
Change-Id: Iaacbcc76809a3aa536e9897770831dcbcb6c8245
Reviewed-on: https://go-review.googlesource.com/47831
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Currently only the rwmutex write lock prevents descheduling. The read
lock does not. This leads to the following situation:
1. A reader acquires the lock and gets descheduled.
2. GOMAXPROCS writers attempt to acquire the lock (or at least one
writer does, followed by readers). This blocks all of the Ps.
3. There is no 3. The descheduled reader never gets to run again
because there are no Ps, so it never releases the lock and the system
deadlocks.
Fix this by preventing descheduling while holding the read lock. This
requires also rewriting TestParallelRWMutexReaders to always create
enough GOMAXPROCS and to use non-blocking operations for
synchronization.
Fixes#20903.
Change-Id: Ibd460663a7e5a555be5490e13b2eaaa295fac39f
Reviewed-on: https://go-review.googlesource.com/47632
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The name LabelList was changed to LabelSet during the development of the
proposal [1], except in one function comment. This commit fixes that.
Fixes#20905.
[1] https://github.com/golang/go/issues/17280
Change-Id: Id4f48d59d7d513fa24b2e42795c2baa5ceb78f36
Reviewed-on: https://go-review.googlesource.com/47470
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
mheap.allocLarge just calls bestFitTreap and is the only caller of
bestFitTreap. Flatten these into a single function. Also fix their
comments: allocLarge claims to return exactly npages but can in fact
return a larger span, and h.freelarge is not in fact indexed by span
start address.
Change-Id: Ia20112bdc46643a501ea82ea77c58596bc96f125
Reviewed-on: https://go-review.googlesource.com/47315
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
The Func type has allowed calling the Func.Name method on a nil pointer
since Go1.2, where it returned an empty string. A regression caused by
CL/37331 caused this behavior to change. This breaks code that lazily
does runtime.FuncForPC(myPtr).Name() without first checking that myPtr
is actually non-nil.
Fixes#20872
Change-Id: Iae9a2ebabca5e9d1f5a2cdaf2f30e9c6198fec4f
Reviewed-on: https://go-review.googlesource.com/47354
Reviewed-by: Marvin Stenger <marvin.stenger94@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Currently the execLock is a mutex, which has the unfortunate
side-effect of serializing all thread creation. This replaces it with
an rwmutex so threads can be created in parallel, but exec still
blocks thread creation.
Fixes#20738.
Change-Id: Ia8f30a92053c3d28af460b0da71176abe5fd074b
Reviewed-on: https://go-review.googlesource.com/47072
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Currently runtime.rwmutex is written to block the calling goroutine
rather than the calling thread. However, rwmutex was intended to be
used in the scheduler, which means it needs to be a thread-level
synchronization primitive.
Hence, this modifies rwmutex to synchronize threads instead of
goroutines. This has the consequence of making it write-barrier-free,
which is also important for using it in the scheduler.
The implementation makes three changes: it replaces the "w" semaphore
with a mutex, since this was all it was being used for anyway; it
replaces "writerSem" with a single pending M that parks on its note;
and it replaces "readerSem" with a list of Ms that park on their notes
plus a pass count that together emulate a counting semaphore. I
model-checked the safety and liveness of this implementation through
>1 billion schedules.
For #20738.
Change-Id: I3cf5a18c266a96a3f38165083812803510217787
Reviewed-on: https://go-review.googlesource.com/47071
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
When the dedicated mark worker runs, the scheduler won't run on that P
again until GC runs out of mark work. As a result, any goroutines in
that P's local run queue are stranded until another P steals them. In
a normally operating system this may take a long time, and in a 100%
busy system, the scheduler never attempts to steal from another P.
Fix this by draining the local run queue into the global run queue if
the dedicated mark worker has run for long enough. We don't do this
immediately upon scheduling the dedicated mark worker in order to
avoid destroying locality if the mark worker runs for a short time.
Instead, the scheduler delays draining the run queue until the mark
worker gets its first preemption request (and otherwise ignores the
preemption request).
Fixes#20011.
Change-Id: I13067194b2f062b8bdef25cb75e4143b7fb6bb73
Reviewed-on: https://go-review.googlesource.com/46610
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
When Stop is called on a channel, wait until all signals have been
delivered to the channel before returning.
Use atomic operations in sigqueue to communicate more reliably between
the os/signal goroutine and the signal handler.
Fixes#14571
Change-Id: I6c5a9eea1cff85e37a34dffe96f4bb2699e12c6e
Reviewed-on: https://go-review.googlesource.com/46003
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Linux's execve has (at the time of writing, and since v2.6.30) a bug when it ran
concurrently with clone, in that it would fail to set up some datastructures if
the thread count before and after some steps differed. This is described better
and in more detail by Colin King in Launchpad¹ and kernel² bugs. When a program
written in Go runtime.Exec's a setuid binary, this issue may cause the resulting
process to not have the expected uid. This patch works around the issue by using
a mutex to serialize exec and clone.
1. https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1672819
2. https://bugzilla.kernel.org/show_bug.cgi?id=195453Fixes#19546
Change-Id: I126e87d1d9ce3be5ea4ec9c7ffe13f92e087903d
Reviewed-on: https://go-review.googlesource.com/43713
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This is a runtime version of sync.RWMutex that can be used by code in
the runtime package. The type is not quite the same, in that the zero
value is not valid.
For future use by CL 43713.
Updates #19546
Change-Id: I431eb3688add16ce1274dab97285f555b72735bf
Reviewed-on: https://go-review.googlesource.com/45991
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
They were failing when run on 32bit RFS, with 32bit gdb.
(mips64 builder now has 64bit RFS, with gdb 7.9.)
Leaving TestGdbPythonCgo disabled, it behaves as described in #18784.
Fixes#18173
Change-Id: I3c438cd5850b7bfd118ac6396f40c1208bac8c2d
Reviewed-on: https://go-review.googlesource.com/45874
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
These are used by DIV[U] and MOD[U] assembly instructions.
Add a test in the stdlib so we actually exercise linking
to these routines.
Update #19507
Change-Id: I0d8e19a53e3744abc0c661ea95486f94ec67585e
Reviewed-on: https://go-review.googlesource.com/45703
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Also add runtime· prefixes to the code that is still used.
Fixes#19507
Change-Id: Ib6da6b2a9e398061d3f93958ee1258295b6cc33b
Reviewed-on: https://go-review.googlesource.com/45699
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Currently, semrelease1 readies the next waiter before recording a
mutex event. However, if the next waiter is expecting to look at the
mutex profile, as is the case in TestMutexProfile, this may delay
recording the event too much.
Swap the order of these operations so semrelease1 records the mutex
event before readying the next waiter. This also means readying the
next waiter is the very last thing semrelease1 does, which seems
appropriate.
Fixes#19139.
Change-Id: I1a62063599fdb5d49bd86061a180c0a2d659474b
Reviewed-on: https://go-review.googlesource.com/45751
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Peter Weinberger <pjw@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Block all signals during a fork. In the parent process, after the
fork, restore the signal mask. In the child process, reset all
currently handled signals to the default handler, and then restore the
signal mask.
The effect of this is that the child will be operating using the same
signal regime as the program it is about to exec, as exec resets all
non-ignored signals to the default, and preserves the signal mask.
We do this so that in the case of a signal sent to the process group,
the child process will not try to run a signal handler while in the
precarious state after a fork.
Fixes#18600.
Change-Id: I9f39aaa3884035908d687ee323c975f349d5faaa
Reviewed-on: https://go-review.googlesource.com/45471
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
I was surprised to see readvarint show up in a cpu profile.
Use a few simple optimizations to speed up stack copying:
* Avoid making a copy of the cache.entries array or any of its elements.
* Use a shift instead of a signed division in stackmapdata.
* Change readvarint to return the number of bytes consumed
rather than an updated slice.
* Make some minor optimizations to readvarint to help the compiler.
* Avoid called readvarint when the value fits in a single byte.
The first and last optimizations are the most significant,
although they all contribute a little.
Add a benchmark for stack copying that includes lots of different
functions in a recursive loop, to bust the cache.
This might speed up other runtime operations as well;
I only benchmarked stack copying.
name old time/op new time/op delta
StackCopy-8 96.4ms ± 2% 82.7ms ± 1% -14.24% (p=0.000 n=20+19)
StackCopyNoCache-8 167ms ± 1% 131ms ± 1% -21.58% (p=0.000 n=20+20)
Change-Id: I13d5c455c65073c73b656acad86cf8e8e3c9807b
Reviewed-on: https://go-review.googlesource.com/43150
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
There are currently two arrays indexed by P ID: allp and pdesc.
Consolidate these by moving the pdesc fields into type p so they can
be indexed off allp along with all other per-P state.
For #15131.
Change-Id: Ib6c4e6e7612281a1171ba4a0d62e52fd59e960b4
Reviewed-on: https://go-review.googlesource.com/45572
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently MaxGomaxprocs is 256. The previous CL saved enough per-P
static space that we can quadruple MaxGomaxprocs (and hence the static
size of allp) and still come out ahead.
This is safe for Go 1.9. In Go 1.10 we'll eliminate the hard-coded
limit entirely.
Updates #15131.
Change-Id: I919ea821c1ce64c27812541dccd7cd7db4122d16
Reviewed-on: https://go-review.googlesource.com/45673
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Back in the day, allp was just a pointer to an array. As a result, the
runtime has a few loops of the form:
for i := 0; ; i++ {
p := allp[i]
if p == nil {
break
}
...
}
This is silly now because it requires that allp be one longer than the
maximum possible number of Ps, but now that allp is in Go it has a
length.
Replace these with range loops.
Change-Id: I91ef4bc7bd3c9d4fda2264f4aa1b1d0271d7f578
Reviewed-on: https://go-review.googlesource.com/45571
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
ARM currently does not use a hardware yield instruction in the spin
loop in procyield because the YIELD instruction was only added in
ARMv6K. However, it appears earlier ARM chips will interpret the YIELD
encoding as an effective NOP (specifically an MSR instruction that
ultimately has no effect on the CPSR register).
Hence, use YIELD in procyield on ARM since it should be, at worst,
harmless.
Fixes#16663.
Change-Id: Id1787ac48862b785b92c28f1ac84cb4908d2173d
Reviewed-on: https://go-review.googlesource.com/45250
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
If we're in a situation where printing the fp and sp in the traceback
is useful, it's almost certainly also useful to print the PC.
Change-Id: Ie48a0d5de8a54b5b90ab1d18638a897958e48f70
Reviewed-on: https://go-review.googlesource.com/45210
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Both runtime.exit and syscall.Exit call Windows ExitProcess.
But recently (CL 34616) runtime.exit was changed to ignore
Windows CreateThread errors if ExitProcess is called.
This CL adjusts syscall.Exit to do the same.
Fixes#18253 (maybe)
Change-Id: I6496c31b01e7c7d73b69c0b2ae33ed7fbe06736b
Reviewed-on: https://go-review.googlesource.com/45115
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
This adds diagnostics so we can tell if the finalizer has started, in
addition to whether or not it has finished.
Updates #19381.
Change-Id: Icb7b1b0380c9ad1128b17074828945511a6cca5d
Reviewed-on: https://go-review.googlesource.com/45138
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
runtime.GC no longer triggers a STW GC. This fixes the description of
GODEBUG=gctrace=1 so it doesn't claim otherwise.
Change-Id: Ibd34a55c5ae7b5eda5c2393b9a6674bdf1d51eb3
Reviewed-on: https://go-review.googlesource.com/45131
Reviewed-by: Rick Hudson <rlh@golang.org>
The current implementation of "goroutine N cmd" assumes it can get
goroutine N's state from the goroutine's sched buffer. But this only
works if the goroutine is blocked. Extend find_goroutine so that, if
there is no saved scheduler state for a goorutine, it tries to find
the thread the goroutine is running on and use the thread's current
register state. We also extend find_goroutine to understand saved
syscall register state.
Fixes#13887.
Change-Id: I739008a8987471deaa4a9da918655e4042cf969b
Reviewed-on: https://go-review.googlesource.com/45031
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Currently the extra Ms created for cgo callbacks have a corresponding
G that's kept in syscall state with only a call to goexit on its
stack. This leads to confusing output from runtime.NumGoroutines and
in tracebacks:
goroutine 17 [syscall, locked to thread]:
runtime.goexit()
.../src/runtime/asm_amd64.s:2197 +0x1
Fix this by putting this goroutine into state _Gdead when it's not in
use instead of _Gsyscall. To keep the goroutine counts correct, we
also add one to sched.ngsys while the goroutine is in _Gdead. The
effect of this is as if the goroutine simply doesn't exist when it's
not in use.
Fixes#16631.
Fixes#16714.
Change-Id: Ieae08a2febd4b3d00bef5c23fd6ca88fb2bb0087
Reviewed-on: https://go-review.googlesource.com/45030
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The test is inherently racy, and for me fails about 0.05% of the time.
So only fail the test if it fails ten times in a row.
Fixes#20594
Change-Id: I3b3f7598f2196f7406f1a3937f38f21ff0c0e4b5
Reviewed-on: https://go-review.googlesource.com/45020
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
For cgo programs on linux-amd64 we call the C function mmap.
This supports programs such as the C memory sanitizer that need to
intercept all calls to mmap. It turns out that there are programs that
intercept both mmap and munmap, or that at least expect that if they
intercept mmap, they also intercept munmap. So, if we permit mmap
to be intercepted, also permit munmap to be intercepted.
No test, as it requires two odd things: a C program that intercepts
mmap and munmap, and a Go program that calls munmap.
Change-Id: Iec33f47d59f70dbb7463fd12d30728c24cd4face
Reviewed-on: https://go-review.googlesource.com/45016
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Try to avoid a race between the main goroutine exiting and a panic
occurring. Don't try too hard, to avoid hanging.
Updates #3934Fixes#20018
Change-Id: I57a02b6d795d2a61f1cadd137ce097145280ece7
Reviewed-on: https://go-review.googlesource.com/41052
Reviewed-by: Austin Clements <austin@google.com>
C code expects CR2, CR3, and CR4 to be preserved across function calls.
Preserve the entire CR register across function calls in
_rt0_ppc64le_linux_lib and crosscall2. The standard ppc64le call frame
uses 8(R1) as the place to save CR; emulate that.
It's hard to write a reliable test for this as it requires writing C
code that sets CR2, CR3, or CR4 across a call to a Go function.
Change-Id: If39e771a5b574602b848227312e83598fe74eab7
Reviewed-on: https://go-review.googlesource.com/44733
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Carlos Eduardo Seo <cseo@linux.vnet.ibm.com>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
Since TestPingPongHog tests the scheduler, it's ultimately
probabilistic. Currently, it requires the result be at most of factor
of 2 off of the ideal. It turns out this isn't quite enough in
practice, with factors on 1000 iterations on linux/amd64 ranging from
0.48 to 2.5. If the test were failing, we would expect a factor closer
to 1000X, so it's pretty safe to expand the accepted factor from 2 to
5.
Fixes#20494.
Change-Id: If8f2e96194fe66f1fb981a965d1167fe74ff38d7
Reviewed-on: https://go-review.googlesource.com/44859
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
key32 is called between entersyscallblock and exitsyscall
stack split may occur if disable inlining and the G is preempted
Fix the problem by describing key32 as nosplit function
Fixes#20510
Change-Id: I1f0787995936f34ef0052cf79fde036f1b338865
Reviewed-on: https://go-review.googlesource.com/44390
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
cmd/compile/internal/ld/decodesym.go is now
cmd/link/internal/ld/decodesym.go
Change-Id: I16ec5c89aa3507e70676c2b50d70f1fde533a085
Reviewed-on: https://go-review.googlesource.com/44373
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This avoids false-positive TSAN reports when using the C sigaction
function to read handlers registered by the Go runtime.
(Unfortunately, I can't seem to coax the runtime into reproducing the
failure in a small unit-test.)
Change-Id: I744279a163708e24b1fbe296ca691935c394b5f3
Reviewed-on: https://go-review.googlesource.com/44270
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Currently, the heap arena allocator allocates monotonically increasing
addresses. This is fine on 64-bit where we stake out a giant block of
the address space for ourselves and start at the beginning of it, but
on 32-bit the arena starts at address 0 but we start allocating from
wherever the OS feels like giving us memory. We can generally hint the
OS to start us at a low address, but this doesn't always work.
As a result, on 32-bit, if the OS gives us an arena block that's lower
than the current block we're allocating from, we simply say "thanks
but no thanks", return the whole (256MB!) block of memory, and then
take a fallback path that mmaps just the amount of memory we need
(which may be as little as 8K).
We have to do this because mheap_.arena_used is *both* the highest
used address in the arena and the next address we allocate from.
Fix all of this by separating the second role of arena_used out into a
new field called arena_alloc. This lets us accept any arena block the
OS gives us. This also slightly changes the invariants around
arena_end. Previously, we ensured arena_used <= arena_end, but this
was related to arena_used's second role, so the new invariant is
arena_alloc <= arena_end. As a result, we no longer necessarily update
arena_end when we're updating arena_used.
Fixes#20259 properly. (Unlike the original fix, this one should not
be cherry-picked to Go 1.8.)
This is reasonably low risk. I verified several key properties of the
32-bit code path with both 4K and 64K physical pages using a symbolic
model and the change does not materially affect 64-bit (arena_used ==
arena_alloc on 64-bit). The only oddity is that we no longer call
setArenaUsed with racemap == false to indicate that we're creating a
hole in the address space, but this only happened in a 32-bit-only
code path, and the race detector require 64-bit, so this never
mattered anyway.
Change-Id: Ib1334007933e615166bac4159bf357ae06ec6a25
Reviewed-on: https://go-review.googlesource.com/44010
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
